The present invention relates to a pin insertion and pulling device, more commonly known as a pin puller, particularly a pin puller that can be used to manipulate pins used for connecting large pieces of machinery together, such as the connections on large lift cranes.
Mobile lift cranes typically include a carbody having moveable ground engaging members; a rotating bed rotatably connected to the carbody such that the rotating bed can swing with respect to the ground engaging members; a boom pivotally mounted on a front portion of the rotating bed, with a load hoist line extending therefrom, and counterweight to help balance the crane when the crane lifts a load. Additionally, when the crane needs to work on particularly high buildings or structures, or in restricted spaces, a luffing jib pivotally mounted at the top of the boom may be extended out to provide required reach. When the luffing jib is employed, one or more luffing jib struts are connected to the top of the boom or bottom of the luffing jib. These struts support the luffing jib rigging and backstay straps, providing a moment arm about which force can be applied to raise the jib and support a load being lifted by the luffing jib.
Since the crane will be used in various locations, it needs to be designed so that it can be transported from one job site to the next. This usually requires that the crane be dismantled into components that are of a size and weight that they can be transported by truck within highway transportation limits. The ease with which the crane can be dismantled and set up has an impact on the total cost of using the crane. Thus, to the extent that fewer man-hours are needed to set up the crane, there is a direct advantage to the crane owner or renter.
Many of the connections that are used when assembling a crane involve placing a pin through holes of two aligned connectors, resulting in a pinned connection. Frequently these connections come in pairs. For example, a boom is hinged to the rotating bed through two pins that connect the boom butt to the rotating bed. Crawlers are often pinned at the ends of legs of a carbody. Lattice members making up columns on the crane are pinned together. For example, a luffing jib strut may be made from two or more sections that are transported to a job site and connected together. However; in some instances the luffing jib strut may be lifted while it is folded, connected on only one side, and when it is ready to be deployed it has to be lifted to where it is straight and then two pills inserted to complete the connection of the two lattice sections making up the luffing jib strut.
Pin pullers are linear actuating devices that push or pull pins into and out of a working configuration when pinning multiple structural members together. They are commonly seen on heavy lift cranes and other heavy equipment when pins get too large to handle manually, the pin connection is in a hard to reach location, or for ease of equipment assembly. Pin pullers are often but not limited to being activated with linearly acting hydraulic or pneumatic cylinders. Sometimes these pin pullers are dedicated to moving just a single pin, and stay attached to the crane next to the pin while the crane is operated. Other times the pin puller is portable, and can be mounted at different places on the crane during assembly and disassembly operations.
Especially when the pin pullers are used in one dedicated place on the crane, there is a need to mount the pin puller to the connector to which the pin is being inserted or from which it is being extracted during a disassembly operation. The connector itself may be fabricated or cast and then machined. Because the pins often carry loads through the pins, the pins must fit tight in the connections. As a result, the pins, and any associated pin puller, must be centered with respect to the holes the pin is inserted in. This often requires precise machining and tolerances when it comes to mounting the pin puller to the connector. Further, the connector itself may need to be larger than is necessary for connecting the crane parts together just so that there is room and structure to mount the pin puller to the connector, since that mounting has to be substantial enough that the pin puller can exert the required force to move the pin into and out of its working position, such as extending through multiple holes in adjacent connectors.
For example, in a pin puller used in a carbody-to-crawler connection on a known mobile lift crane, one hydraulic cylinder is threaded directly to a single pin. A support frame is bolted and piloted via machined surfaces directly to the parent component (carbody). The hydraulic cylinder bolts to this frame to transmit the cylinder force of inserting or removing of the pin to the parent component via the bolts attaching the support frame to the parent component. The support frame also prevents axial rotation of the hydraulic cylinder to prevent entanglement of the supply and return hydraulic lines going to the hydraulic cylinder. Even though the pin may be piloted, the pin is not self-centering because the pin puller is rigidly attached to the parent component. As a result, pin centering is only achieved through accurate machining of the pin puller component itself, and requires much additional machining to achieve accurate attachment to the parent component.